(a) Field of the Invention
This invention relates to an electroflash controlling circuit for electrically controlled focal plane shutters.
(b) Description of the Prior Art
A type of electroflash controlling circuit for electric shutters wherein an electric signal for closing a shutter is utilized directly for an electroflash triggering signal has been already suggested. However, this type has such defect as is mentioned below. Now, an electrically controlled focal plane shutter provided with a front blade group and rear blade group in the case that the shutter speed is set at 1/125 second (the rear blade group will begin to run after the lapse of 7.8 m.s. after the front blade group begins to run) shall be exemplified and explained. In such case, as shown in FIG. 4, due to mechanical and magnetic operation delays, it will take a time of 5 m.s. before both front blade group and rear blade group actually begin to run after respective running starting electric signals or release signals are issued. The time required for the front blade group to reach the fully opened position from the position in which it perfectly covers the exposure aperture and the time required for the rear blade group to reach the perfectly covering position from the position in which it fully opens the exposure aperture are both about 6 m.s. Therefore, if the electric signal for starting the running of the rear blade group is utilized directly for the electroflash triggering signal, it will be issued as a result while the front blade group is running to open the exposure aperture and the flash lamp will flash before the front blade group reaches the fully opened position. Such defect will occur also in a type of focal plane shutter wherein the front blade group is mechanically started to run by the operation of a release button.